For countless generations, man in his perpetual quest to subdue the forces of nature has been little concerned with ecological consequences. Increasing population with the concomitant urban sprawl has resulted in the denuding of forests, damming of rivers and streams and the filling of marshlands. This conduct has greatly affected the delicate balance of the earth's ecosystem. Consequently, many biological and zoological forms of life are faced with inevitable extinction because of dwindling natural habitats.
Threatened flora and fauna have few avenues available to avert the tide of "progress" and many of these approaches are not feasible because of the amount of time involved. For example, natural selection, which would develop species immune to man's alteration of the environment, is a slow gradual process. Because of rapid deterioration of the environment, many species will be extinct long before this biological phenomenon will have any consequences. A drastic alternative, which is not feasible, would entail a moratorium on further development coupled with attempts to reduce much of man's present unfavorable impact on the environment.
The only viable alternative presently available to these approaches is to formulate a means whereby the plants and animals may live in a protected, though unfortunately considerably limited environment. Thus, we find many zoological gardens attempting to provide threatened species with a simulated habitat. By faithfully copying the creatures natural home, the stresses caused by man's encroachment are lessened and the animal is more apt to procreate and continue the species. However, this has limitations, the most notable being financial. The public is not quite ready for the protection of the earth's non-human inhabitants on a large scale. A further limitation on this system of surrogate homes is that many animals do not spend their whole life in one habitat. Among these are salmon who spawn their eggs near the head waters of fresh water streams and rivers but spend the bulk of their adult lives in the ocean. As a result, the costs of duplicating these multiple native environments is prohibitive.
The influx of people to the Pacific Northwest and Alaska has brought about numerous problems for salmon. Many of the streams traveled to spawn their eggs have been dammed. Others have become so polluted that no living creature can survive. Still others have become too shallow or diverted from their natural course because of the ever increasing needs for water in domestic and industrial use. Consequently, the available streams for spawning of salmon eggs has dwindled. The salmon population is also beset with additional deletorious factors such as predator pressures. Predator difficulties seem to be magnified when the salmon population undergoes the stress of extraordinary natural and man-made environmental influences.
In order to rejuvenate the salmon population several attempts have been made to overcome the problem of loss of natural spawning grounds. Unfortunately, however, numerous unsolved problems remained. For instance, in U.S. Pat. No. 3,464,385 to Pellett, the patentee teaches a method of rehabilitating salmon spawning streams by bubbling air through the stream bed gravel from a number of points periodically spaced throughout the spawning area. The added oxygen was primarily used to offset silt suffocation. While this approach may have some beneficial aspects, it does not, however, radically increase the production of salmon. Furthermore, it requires placing the aerator under the bed of the stream. This may entail temporarily damming the stream or diverting it from its bed. Even if the device were set up without disturbing the stream's course, its installation is still cumbersome.
Other attempts have been made to increase the salmon population. Most significant of these are the experiments undertaken at Abernathy Creek near Longview, Wash. The results of these experiments are described in an article by Allen E. Thomas entitled Effect of Egg Development at Planting on Chinook Salmon Survival, 37 Progressive Fish-Culturist 231 (October 1975) and in a joint article by Allen E. Thomas and J. M. Shelton entitled Operation of Abernathy Channel for Incubation of Salmon Eggs, Technical Papers of the Bureau of Sport Fisheries and Wildlife published by the U.S. Department of the Interior, the disclosures of which are incorporated by reference.
At Abernathy Channel, an artificial spawning and incubation channel, salmon and trout eggs were deposited in trenches in natural spawning gravel or artifical incubation channels. Three types of salmon eggs were planted. Unwater-hardened eggs were planted immediately after fertilization. Water hardened eggs had been fertilized, washed free of silt and water hardened for one hour before planting. After the eggs in the third group were washed and water hardened in hatchery troughs, they were incubated until the eyed stage was reached and then planted. The survival percentages of the salmon to the migrant fry stage was 50.1 percent from water unhardened eggs, 37.6 percent from water hardened, and 73.4 percent from eyed.
The difficulty with the Abernathy Creek experiment was that it required construction of a special incubation channel and a settling pond for siltation. The channel had to be designed so that the build up of silt was prevented because of silt's deletorious effect on the incubation and hatching of salmon eggs. Also, care had to be taken to prevent adult salmon from entering the channel. The major difficulty was the time consuming trench digging in the channel for the planting of the salmonid eggs and the construction of the settling pond. It is evident from the results of the Abernathy Creek experiment that there was a critical need for a means of planting salmon eggs that did not require the expense and labor of a specially built and designed channel.
It is an object of this invention to provide a method and apparatus for the planting of salmon eggs which combines ease of operation, portability and high yields of fry.